The structure, distribution and function of G protein-coupled receptors are being studied. Several genes and cDNAs for receptors expressed in brain or elsewhere have been cloned. The distribution of their mRNAs have been determined by northern blots or in situ hybridization histochemistry. The chromosomal location of the human genes has been determined. Expression of the receptors in mammalian cells has allowed their pharmacological properties to be studied. Site-directed mutagenesis of the CB1 cannabinoid receptor is being used to test molecular models of the receptor. Transgenic mice with either the CB1 or CB2 cannabinoid receptor knocked out are being created to study the physiological role of these receptors. The structure of the CB1 human, rat and mouse receptor gene is being studied in order to characterize what appears to be discrete multiple promoters.